I have a 99 f-150 5.4 i have had intermittent rough idle since i got it a little over a year ago. now it seems to throw up p0172 and p0175 codes for system to rich when it does this. I cleaned the throttle body and EGR (wasnt clogged), replaced the IAC, fuel filter, pvc valve, IAT and cleared the keep alive memory to no avail, im due up for smog in the next few weeks and am gonna change the plugs this weekend. Anything else seems to be pointing at the MAF, i tested it today and the return signal is in the .15 - .30 range , book says .34 minimum, should i just bite the bullet and replace the MAF, i never had a code comeup for it but it appears below its range. any other suggestions would be great. thanks

patrick

 

You need to take the MAF apart and clean the hot wire sensor with carb cleaner spray. The hot wire will get dirty over time and cause those codes. It will run like a new one probably. No need to replace it, yet.